October 15, 2015: received a Logitech M558 Bluetooth mouse from the Apple online Store. It's allegedly designed to go for at least 12 months on a pair of alkaline AA cells. Granted, I've not used it daily, as it's paired with the MacBook Air & I normally use the trackpad but I just tested the cells & both are still around 90% of original capacity. I see little reason to dispute the 12 month battery life claim.